The present invention relates to magnetic disk drive data storage devices with multiple disks stacked on a spindle, and more particularly to rotary actuators for such devices and the mounting of certain electrical circuitry on the actuators.
Designers of computer data storage products are well aware of the constant effort to improve data storage efficiency, particularly in terms of increasing the amount of data stored in a limited physical space to enhance data storage capacities. This goal is well served by disk drives having multiple rigid disks on a spindle, axially aligned in a stack for simultaneous rotation. These drives typically include rotary actuators to read and record data. The rotary actuator includes a pivotally mounted carriage, with multiple transducer support arms extended radially of the carriage and supporting data transducers at their free ends. As the carriage pivots, the transducers are carried arcuately, and generally radially relative to data recording surfaces of the disks.
Typically, one of the recording surfaces is dedicated to storage of servo positioning information. The transducer associated with this surface provides rotary actuator position information used by the remaining transducers when reading and recording data on their associated recording surfaces.
Traditionally, the electrical circuitry used in reading and recording data is mounted on each support arm near the associated transducer. As stacks of disks and rotary actuators become more compact, and as improved manufacturing techniques have enabled the manufacture of unitary head arm assemblies incorporating the carriage and arms, the traditional mounting of the circuitry has become correspondingly more difficult. U.S. Pat. application Ser. No. 07/569,818, filed Aug. 20, 1990 and assigned to the assignee of the parent application, discloses a circuit board mounted to the carriage parallel to the actuator pivot axis. The circuit board, frequently referred to as a matrix board, cooperates with multiple transducers through multiple conductors. This board replaces multiple preamp circuits mounted on each arm, thus to substantially reduce manufacturing cost. A portion of the circuit board extends away from the carriage along one side of a stack of transducer support arms. This extension along the arms is desirable, in that noise is reduced as the circuitry is disposed nearer to the transducers. The section of the circuit board extended along the support arms behaves as a cantilever. It is not fixed to the arms, although it may contact the arms. The result is a tendency of the extended section to vibrate, become separated from the support arms and then collide with the arms, whenever the head arm assembly is rapidly accelerated or decelerated during normal head positioning, particularly track seeking.
Another improvement concerning head positioning in rotary actuators is disclosed in U.S. Pat. No. 4,814,908 (Schmitz). A heating element is embedded along at least one of the side edges of a transducer support arm. Selected application of heat to the heating element results in a controlled linear expansion of the support arm, for slight (microinch range) arcuate movement of a transducer carried by the arm. This affords a micro-positioning adjustment for improved track following.
As disclosed in the aforementioned U.S. Pat. application Ser. No. 07/569,818, the micro-positioning improvement can be utilized with a stack of transducer support arms, by mounting a flex circuit along the carriage, between the carriage and the circuit board devoted to data reading and recording operations. Electrically insulative spacer separate the flex circuit from the carriage, and on the flex circuit, from the circuit board. To ensure adequate heat dissipation and to ensure that heat from the circuit board does not interfere with the operation of individual heating elements along the support arms, the circuit board is maintained spaced apart from the arms, which of course increases the tendencies of circuit board vibration and impact against the transducer support arms, both of which are detrimental to transducer positioning accuracy.
Therefore, it is an object of the present invention to provide a rotary actuator in which a read/write circuit package is mounted along a head arm assembly, with a section of the package extended away from the carriage along the transducer support arms in cantilever fashion, yet positively maintained against the support arms.
Another object is to provide a magnetic disk drive rotary actuator in which the read/write circuit is maintained in a stable, contacting and non-fixed relation to a plurality of transducer support arms.
Yet another object is to provide a means for supporting a read/write circuit package and a heating element control circuit package along one side of a rotary actuator including multiple stacked transducer support arms, in which these circuit packages are spaced apart from one another yet positively maintained against vibration and shock due to impact of either circuit against the transducer support arms.